Summary
Open WebUI: Account takeover via OAuth token exchange accepting tokens issued to any client
The OAuth token exchange endpoint accepts a raw provider access token and validates it by calling the provider's userinfo endpoint. A userinfo endpoint reports only that a token is valid, never which OAuth client it was issued to, and the endpoint performed no audience or client check of its own. Anyone holding an access token minted for any client registered with the same provider could exchange it for an Open WebUI session as that token's user, including applications the operator does not control and has never authorised.
Preconditions
ENABLE_OAUTH_TOKEN_EXCHANGE=True. Disabled by default, so a stock deployment is not affected.- The victim already has an Open WebUI account. The endpoint does not create users.
- The attacker can obtain a provider access token for the victim, typically by having them sign in to an unrelated OAuth application on the same provider. On public providers, registering that application is self-service.
- The subject identifier the attacker's client observes matches the one stored on the victim's account. Google, GitHub, Okta and self-hosted OIDC servers in default configuration issue a subject that is stable across all clients and are directly affected. Microsoft Entra ID issues per-application subjects, so the match fails there unless
OAUTH_MERGE_ACCOUNTS_BY_EMAILis enabled orOAUTH_SUB_CLAIMpoints at a globally stable claim such asoid. OAUTH_ALLOWED_DOMAINSis enforced on this endpoint but does not constrain the attack, because the impersonated user is a legitimate member of an allowed domain.
Root cause
backend/open_webui/routers/auths.py,token_exchange(POST /api/v1/auths/oauth/{provider}/token/exchange)
Token exchange skips the authorization-code step entirely and trusts a token supplied by the caller. The only validation performed was a userinfo lookup, which answers whether a token is valid rather than who issued it, so the endpoint had no way to distinguish a token minted for Open WebUI from one minted for an unrelated application.
Proof of concept
Reproduced against a mock OIDC provider serving two tokens for the same end user, minted for two different clients, with OAUTH_ALLOWED_DOMAINS=corp.example actively enforced.
| Case | Token | Result |
|---|---|---|
| Control | not recognised by the provider | 400 rejected |
| Outsider's own account, non-allowed domain | minted for attacker-evil-app |
403 blocked by domain allowlist |
| Victim's account, foreign client | minted for attacker-evil-app |
200, session issued for [email protected] |
The issued session token was confirmed usable: GET /api/v1/auths/ returned 200 authenticated as the victim. The provider log recorded the token as minted for client_id='attacker-evil-app', while Open WebUI's own client is openwebui-client-id.
Credits
Reported by @Classic298.
Impact
Full account takeover of any user whose provider access token the attacker can obtain. The endpoint applies no role gating, so the issued session carries the target account's role, and a targeted administrator yields an administrator session. The victim never interacts with Open WebUI and has no opportunity to notice.
The standard OAuth callback is not affected. It obtains its token through an authorization-code exchange authenticated with the client secret, so the token is inherently bound to Open WebUI's own client, and the ID token's audience is validated.
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
CVE-2026-70482 has a CVSS score of 8.1 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.11.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in 0.11.0. The endpoint now resolves which OAuth client a presented token was issued to through RFC 7662 token introspection, and rejects tokens minted for any client not named in OAUTH_TOKEN_EXCHANGE_TRUSTED_CLIENT_IDS. Only the introspected client_id is honoured; the aud field is ignored, because it names intended resource servers rather than the issuing client and several providers let any client place another client's identifier there.
Upgrading alone is not sufficient. The check is opt-in: with OAUTH_TOKEN_EXCHANGE_TRUSTED_CLIENT_IDS unset the endpoint behaves as it did before, so any deployment running with ENABLE_OAUTH_TOKEN_EXCHANGE=True must also set that list. It is a deploy-time environment variable and cannot be changed from the admin interface, so a compromised administrator session cannot widen the trust boundary at runtime.
Providers that do not implement RFC 7662 introspection, including Google, Microsoft Entra ID, GitHub and Feishu, cannot be restricted this way at all. On those, token exchange has no safe configuration and should be left disabled.
Frequently Asked Questions
- What is CVE-2026-70482? CVE-2026-70482 is a high-severity improper authentication vulnerability in open-webui (pip), affecting versions >= 0.8.0, < 0.11.0. It is fixed in 0.11.0. The application does not adequately verify the identity of a user, device, or process before granting access.
- How severe is CVE-2026-70482? CVE-2026-70482 has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of open-webui are affected by CVE-2026-70482? open-webui (pip) versions >= 0.8.0, < 0.11.0 is affected.
- Is there a fix for CVE-2026-70482? Yes. CVE-2026-70482 is fixed in 0.11.0. Upgrade to this version or later.
- Is CVE-2026-70482 exploitable, and should I be worried? Whether CVE-2026-70482 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-70482 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-70482? Upgrade
open-webuito 0.11.0 or later.